linux_dsm_epyc7002/arch/xtensa/include/uapi/asm
David Herrmann 28b5ba2aa0 net: introduce SO_PEERGROUPS getsockopt
This adds the new getsockopt(2) option SO_PEERGROUPS on SOL_SOCKET to
retrieve the auxiliary groups of the remote peer. It is designed to
naturally extend SO_PEERCRED. That is, the underlying data is from the
same credentials. Regarding its syntax, it is based on SO_PEERSEC. That
is, if the provided buffer is too small, ERANGE is returned and @optlen
is updated. Otherwise, the information is copied, @optlen is set to the
actual size, and 0 is returned.

While SO_PEERCRED (and thus `struct ucred') already returns the primary
group, it lacks the auxiliary group vector. However, nearly all access
controls (including kernel side VFS and SYSVIPC, but also user-space
polkit, DBus, ...) consider the entire set of groups, rather than just
the primary group. But this is currently not possible with pure
SO_PEERCRED. Instead, user-space has to work around this and query the
system database for the auxiliary groups of a UID retrieved via
SO_PEERCRED.

Unfortunately, there is no race-free way to query the auxiliary groups
of the PID/UID retrieved via SO_PEERCRED. Hence, the current user-space
solution is to use getgrouplist(3p), which itself falls back to NSS and
whatever is configured in nsswitch.conf(3). This effectively checks
which groups we *would* assign to the user if it logged in *now*. On
normal systems it is as easy as reading /etc/group, but with NSS it can
resort to quering network databases (eg., LDAP), using IPC or network
communication.

Long story short: Whenever we want to use auxiliary groups for access
checks on IPC, we need further IPC to talk to the user/group databases,
rather than just relying on SO_PEERCRED and the incoming socket. This
is unfortunate, and might even result in dead-locks if the database
query uses the same IPC as the original request.

So far, those recursions / dead-locks have been avoided by using
primitive IPC for all crucial NSS modules. However, we want to avoid
re-inventing the wheel for each NSS module that might be involved in
user/group queries. Hence, we would preferably make DBus (and other IPC
that supports access-management based on groups) work without resorting
to the user/group database. This new SO_PEERGROUPS ioctl would allow us
to make dbus-daemon work without ever calling into NSS.

Cc: Michal Sekletar <msekleta@redhat.com>
Cc: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-06-21 11:38:41 -04:00
..
auxvec.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
byteorder.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
ioctls.h xtensa/uapi: Add definition of TIOC[SG]RS485 2014-09-09 23:48:57 -07:00
ipcbuf.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
Kbuild uapi: export all headers under uapi directories 2017-05-11 00:21:54 +09:00
mman.h x86/pkeys: Allocation/free syscalls 2016-09-09 13:02:27 +02:00
msgbuf.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
param.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
poll.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
posix_types.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
ptrace.h xtensa: move internal ptrace definitions from uapi/asm to asm 2017-05-01 07:00:10 -07:00
sembuf.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
setup.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
shmbuf.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
sigcontext.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
signal.h xtensa: pull signal definitions from signal-defs.h 2013-02-23 19:12:52 -08:00
socket.h net: introduce SO_PEERGROUPS getsockopt 2017-06-21 11:38:41 -04:00
sockios.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
stat.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
swab.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
termbits.h UAPI: (Scripted) Disintegrate arch/xtensa/include/asm 2012-10-15 21:48:53 -07:00
types.h xtensa: add alternative kernel memory layouts 2016-07-24 06:33:58 +03:00
unistd.h xtensa: wire up statx system call 2017-03-31 16:26:21 -07:00